310 MESSRS. PROUDMAN, DOODSON, AND KENNEDY ON THE DIFFRACTION OF 
Figs. 25 to 28 give the final graphs of Yj + Yfi Zj + Z., 2 , the obtaining of which 
has been the object of the whole work. 
From 0 = 0° to 120° the curve for Zj+Zj is probably correct to 0'2 per cent. ; from 
120° to 150°, to 0 - 5 per cent. ; from 150° to 180°, to 1 per cent. The curve for 
Yj 2 + Y 2 2 is probably correct to 1 per cent, throughout the range. 
These curves are drawn to different scales, as Zj + Zj is approximately constant up 
to 0 — 120°, while Y^ + Y/ has oscillations of increasing amplitude. The curves for 
Yj 2 +Y 2 2 illustrate these oscillations up to the point where the last minimum occurs; 
after this the value of Y x 2 + Y 2 2 increases rapidly to a maximum at 6 = 180°. The 
curves for Zj + Z.j illustrate the behaviour of this function up to 6 = 140°, but do not 
show the last oscillation before the function begins to increase rapidly to its maximum 
at 6 = 180°. For this range data are given in the tables. 
